Mice lacking platelet-collagen receptors exhibit prolonged tail-bleeding times. Tail-bleeding times of wild-type (BalbC and C57Bl/6), α₂β₁^–/–, GPVI-FcRγ^–/–, and GPVI-FcRγ^–/–;α₂β₁^–/– were determined. Approximately 2 mm of tail was cut from unanesthetized mice, the tail immersed in 37°C saline, and the bleeding time recorded as the moment when bleeding ceased. Each point represents an individual animal (n = 10-17). Mouse strain is indicated in parentheses. WT indicates wild type. The horizontal bars indicate the average tail-bleeding times.